Currently, with the image fusion technology, lightness and color of a to-be-inserted image may be consistent with those of a target scenario, making the fused image more natural. The main fusion methods available are the alpha matte method, and the fusion method based on the gradient domain. The method based on alpha matte may realize a fusion of foreground and background by parsing the α parameter (i.e., the ratio of the foreground color to the pixel color), so that the color consistency of a fused area is higher. The fusion method based on the gradient domain is an image editing method well-developed in recent years, well solving the problem that the lightness and the color of the to-be-inserted image have a big difference from those of the target scenario. With the fusion method based on the gradient domain, the color and the lightness gradually change from the fusion boundary to the inside of the image, thereby achieving a smooth transition of color.